MacOS – How to disable the “Your computer time is almost up.” dialog

When parental controls are enabled and computer time setting is set, the controlled user will be shown a dialog 15, 5 and 1 minute(s) before the time is up:

An admin user can add more computer time through this dialog (15 min, 30 min, rest of the day etc.), if he wishes.

Is there a way to disable this dialog? — no mercy!*

I know it's not available through the System Preferences, but is there some sort of hidden setting that can be reached through, e.g. Terminal? Or alternatively, is there a way to automatically send ⌘ + W key combo when a specific dialog appears?

I'm (still) on Snow Leopard, but if some answer would work on Lion, I'm willing to accept it.

_{*) Actually I've enabled parental controls for my sock–puppet account and, because I know the admin password, adding time through this dialog would be just too easy.**}

_{^{**) I also know that, being an admin, I could add more time in many different ways and blocking this dialog wouldn't prevent me adding more time in other ways. But—like I said—adding time through this dialog is too easy.}}